1. Field of the Invention
The present invention relates to solid-state image pickup devices and a method for driving the solid-state image pickup device, and, more particularly, to an X-Y addressing type solid-state image pickup device having an amplification capability at each pixel unit, and a method for driving the same.
2. Description of the Related Art
FIG. 11 shows one of known conventional solid-state image pickup devices, such as the one disclosed in U.S. Pat. No. 5,345,266. The solid-state image pickup device includes a matrix of unit pixels 101 two-dimensionally arranged. A vertical scanning circuit 102 selects rows through vertical scan selection lines 103. A column amplifier 105 is connected to each of vertical signal lines 104. A pixel signal of each unit pixel 101 is stored in the respective column amplifier 105 on a row-by-row basis, while a horizontal scanning circuit 106 selects columns. The solid-state image pickup device thus outputs the signal thereof through a horizontal signal line 107 and a sense amplifier 108.
In the solid-state image pickup device having the above construction, a signal charge for 1H (one horizontal scanning period) is sent to the column amplifiers 105 at one time. The signal charge is once stored in the column amplifier 105 and is then read out. A capacitor of the column amplifier 105 stores a signal, the magnitude of which is subject to variations in a reset level of the column amplifier 105. As a result, variations in characteristics of transistors used in each column amplifier 105 is superimposed on the signal, and appear as a vertical streak, fixed pattern noise (FPN) on screen.
To suppress the vertical streak, fixed noise pattern, a noise canceling circuit using a frame memory is arranged external to the device. The noise canceling circuit stores in advance one of an output signal during a dark period (a noise component) and an output signal during a light time (a video component) in the frame memory on a pixel by pixel basis, and performs an extraction operation between the one output signal and the other output signal to remove the noise component due to the variations in the transistor characteristics. In a camera system using a solid-state image pickup device, the noise canceling circuit using the frame memory needs to be mounted external to the device, and the size of the camera system becomes bulky accordingly.
Accordingly, it is an object of the present invention to provide a solid-state image pickup device that removes a fixed pattern noise and a method for driving the image pickup device.
A solid-state image pickup device of the present invention includes a matrix of unit pixels, and each unit pixel includes a photoelectric converter, and five transistors of a read out transistor, a read out selection transistor, an amplifying transistor, a reset transistor, and an output selection transistor. A plurality of horizontal signal lines are wired to the unit pixels, each on a row-by-row basis, and a single vertical signal line is commonly wired to these horizontal signal lines. The solid-state image pickup device further includes a vertical drive unit which selects the pixels on a row-by-row basis while successively outputting, to the vertical signal line, pixel signals which are output by the pixels to the plurality of the horizontal signal lines, and a horizontal drive unit which feeds a horizontal selection pulse to the read out selection transistor and the output selection transistor at the unit pixel while feeding a reset pulse to the reset transistor.
With the above arrangement, when the vertical drive unit selects one row, the horizontal drive unit feeds a reset pulse to the reset transistor to reset the storage unit, and the reset level by the reset transistor is output to the horizontal signal line through the amplifying transistor. In succession, a horizontal scanning pulse is fed to the read out selection transistor, which then reads out the signal charge photoelectrically converted by the photoelectric converter and stored, into the storage unit. The signal charge is then amplified through the amplifying transistor and is then output to the horizontal signal line as the signal level. The reset level and the signal level are thus fed to the vertical signal line through the horizontal signal line in a point-at-a-time scanning manner.